Catheters are well known in the art for fluid injection and/or removal from a human or animal body. Catheters are typically utilized to relieve urinary obstruction, to relieve severe urinary incontinence, and to monitor urine output in the critically ill patient.
A major problem with catheters has been their tendency to be displaced from the body. Although a number of solutions have been proposed to this problem, none has been entirely successful. For example, a common approach is to provide an expandable balloon at the distal end of the catheter which is inflated after placement of the catheter within a body cavity in order to retain it in position. This popular, self-retaining catheter is called a "Foley" catheter, but it suffers from shortcomings including the need for a separate channel within the catheter wall to inflate the balloon. This additional channel increases the diameter of the catheter and renders it unacceptable where very thin catheters are needed, such as for use in small children. Also, the balloon-type catheters can result in accidental urethral injury due to inflation of the balloon while in the urethra or by accidental extraction of the catheter without first deflating the balloon. The presence of the balloon can cause bladder spasms and discomfort. The large surface area of foreign material within the urinary bladder may promote crystal formation and result in bladder stones. Infection can result from use of balloon-type catheters since drainage from above the balloon allows a sump of urine to remain in the bladder at all times. Moreover, problems may arise with this type of catheter due to inability to deflate the balloon once inflated in a body cavity.
Another type of catheter commonly used is constructed of a flexible tubing which is preformed so that in its relaxed state in the body cavity it assumes a desired shape and is thereby self-retaining. A shortcoming of this catheter is that a stiffening member such as a wire is inserted through the bore of the catheter in order to straighten it for insertion into a body cavity. When the distal end reaches its destination, the wire is retracted and the preshaped distal end assumes its preformed shape. This approach to a self-retaining catheter possesses a number of shortcomings including the fact that the straightening wire is potentially dangerous and usage of the catheter is therefore confined to physicians. This is a substantial limitation to use of the catheter since many times it is desirable to have the catheter inserted by a nurse or technician.